Previously, there is known a valve timing control apparatus that adjusts valve timing of valves, which are opened and closed by a camshaft, by rotating a driven-side rotatable body, which is rotated synchronously with the camshaft, relative to a driving-side rotatable body, which is rotated synchronously with a crankshaft. JP2009-185786A discloses such a valve timing control apparatus that includes a sun gear, which is fixed to the driving-side rotatable body with a bolt, and a planetary gear, which is meshed with an internally toothed portion of the sun gear having internal teeth. The driven-side rotatable body is rotated relative to the driving-side rotatable body through planetary motion of the planet gear. In JP2009-185786A, the sun gear is press fitted to the driving-side rotatable body to limit misalignment of the sun gear relative to the driving-side rotatable body.
In JP2009-185786A, the driving-side rotatable body is press fitted to a radially inner side of each of press fitting projections of the sun gear, which project in the axial direction on a radially outer side of the internally toothed portion of the sun gear. For example, in a case where an axial position of a sprocket formed at an outer wall of the driving-side rotatable body is set to be closer to the sun gear, the fitting relationship between the driving-side rotatable body and the sun gear needs to be reversed. That is, it is required to press fit the sun gear to the radially inner side of the press-fitting projections that project from the driving-side rotatable body in the axial direction.
However, when the fitting relationship between the driving-side rotatable body and the sun gear is reversed in the above-described manner, the sun gear receives an axial compression force from the bolts and is thereby deformed to expand in the radial direction. At this time, radially outward deformation of the sun gear is interfered by the press-fitting projections of the driving-side rotatable body. Thus, the amount of deformation of the sun gear toward the radially inner side becomes larger than the amount of deformation of the sun gear toward the radially outer side. As a result, generations of friction and noise caused by the radially inward deformation of the internally toothed portion of the sun gear occur, and thereby there may possibly be deterioration in the performance and durability of the valve timing control apparatus.